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Formation et extension de macles de déformation dans des nanostructures cfc : simulations numériques

Abstract : For several decades, the elaboration of nano-structured materials tends to develop more and more. Indeed, these materials often show interesting properties, and in particular surprising mechanical properties when compared to their bulk counterparts. For example, nano-twinned or nano-layered metals are known to have ultra-high mechanical strength, good thermal stability, and very good radiation resistance. As the interface spacing decreases to the nanometer-scale, the density of interfaces increases significantly and subsequently the macroscopic properties become largely governed by the interface-defect interactions. In that context, we have studied deformation twin formation and mechanisms of interaction between a new formed twin and a preexisting interface (a twin boundary or a bimetallic interface), using atomistic simulations and a thin film model configuration. First results show the influence of surface steps on mechanical twinning, for a model system without interface. Then we identify a new mechanism leading to the formation of a Lomer dislocation, following the interaction of a newly formed twin and a preexisting twin boundary. By varying the density of surface defects, we show the particular influence of a preexisting twin boundary on twin size and number. Finally, for the Cu/Ag bimetallic system, our results highlight the role of epitaxial dislocations (at the interface) in twin nucleation and extension as well as a direct influence of the interface type in twin propagation.
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Submitted on : Friday, April 9, 2021 - 9:42:13 AM
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  • HAL Id : tel-03193799, version 1

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Romuald Béjaud. Formation et extension de macles de déformation dans des nanostructures cfc : simulations numériques. Matériaux. Université de Poitiers, 2017. Français. ⟨NNT : 2017POIT2318⟩. ⟨tel-03193799⟩

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